1. Field of the Invention
The present invention relates to telecommunications. More particularly, the present invention relates to an ATM-based distributed network switching system for use within a public switched telephone network (PSTN).
2. Background Information
Today's network backbone is a consolidation of dissimilar networks, including, for example, asynchronous transfer mode (ATM), frame relay, time division multiplex (TDM), private line, etc. The variety of networks is necessary to accommodate different types of access, e.g., xDSL, ISDN, line access, etc.
The present day network backbone employs numerous protocols because each type of network requires its own protocols. Even within the voice network alone, there are multiple protocols and thus protocol conversions are required. That is, an incoming protocol, e.g., Bellcore GR-303, communicates with digital loop carriers (DLCs) to control voice channels coming into the switch. Within the switch, a different switch protocol transfers the traffic through the switch. To further complicate the situation, the internal switch protocol of each vendor is proprietary. Another protocol, i.e., a trunk protocol (e.g., Signaling System 7 (SS7)), is necessary to move the traffic from the originating switch to the destination switch. The large number of protocols operating within the network backbone complicates communications across the backbone.
The present day backbone has disadvantages other than a plethora of protocols. For example, each type of network is managed in a different manner with its own management system, often from a different location. Thus, many areas of expertise are required to manage the network backbone. In other words, a large number of engineers, having different skill sets, is required to manage the heterogeneous network.
The present day central office architecture also demands burdensome engineering and management. More specifically, each central office must be managed separately. To compound the problem, each central office has a unique configuration, different from each other central office. For example, different central offices may have different vendor's switches (switch types), as well as different switch hardware configurations. Thus, a variety of personnel, with different skill sets is required to manage a unique central office. In addition, the engineering of facilities and trunks between central offices and their switches consumes a large number of personnel with unique skill sets as well as physical resources.
It has been proposed to replace tandem switches with a distributed architecture, referred to as Voice Trunking over ATM (VTOA), to reduce the number of trunks between central offices and accordingly engineering of trunks between end offices. VTOA is, however, limited to trunk interconnection (that is, service provider's switch interconnection as opposed to customer's access) and still requires the services of Class 5 switches. Consequently, even with VTOA, the network backbone requires multiple protocols and additional hardware to provide all the necessary switch interconnection.
Another problem with today's voice network is that end office Class 5 switches, such as the Lucent 5ESS and Nortel DMS 100, are proprietary switches employing proprietary hardware and software. That is, upgrading and replacing of switches is not an easy task, in part due to this proprietorship. Thus, a need exists for components with a generic hardware implementation that relies upon software and personality cards to provide specific functionality.
The current network architecture does not distribute well within a metropolitan area due to the transport requirements and technology base of the current Class 5 switches. Thus, the current central office based telephony topology is constrained to geographical boundaries and often requires digital loop carriers (DLCs) and other remote telephony units. Therefore, a need exists to replace today's end office Class 5 switches with a distributed switching system. This will allow the extension of the central office switch boundaries to the controlled environment vault (CEV) of the carrier serving area (CSA) or even to the customer premises for medium and large customers.
Thus, a need exists for a streamlined network backbone that allows all kind of access and is managed by a single management system from a single location or a limited number of locations. The management system should be able to converse with all components of the network using a single standardized protocol, significantly reducing the need for protocol conversion. It would also be desirable if proprietary hardware could be eliminated. Such a network would only require expertise in a single area and thus would reduce the personnel required for network management.    Glossary of Acronyms    A-IWF Access Interworking Function    AAL ATM Adaptation Layer    ABR Available Bit Rate    ACM Address Complete Message    ADPCM Adaptive Differential Pulse Code Modulation    ADNSS ATM Based Distributed Network Switching System    ADSL Asymmetric Digital Subscriber Line    AIN Advanced Intelligent Network    ANM Answer Message    ANSI American National Standards Institute    ATM Asynchronous Transfer Mode    BAF Bellcore AMA Format    B-ISUP Broadband ISDN User Part    CAS Channel Associated Signaling    CBR Constant Bit Rate    CCS Common Channel Signaling    CES Circuit Emulation Service    CEV Controlled Environment Vault    CIC Circuit Identification Code    CSA Carrier Serving Area    CS-IWF Control and Signaling Interworking Function    DLC Digital Loop Carrier    DPC Destination Point Code    DS0 Digital Signal Level 0 (64 Kbps digital signal format)    DS1 Digital Signal Level 1 (1.544 Mbps digital signal format)    IAM Initial Address Message    IP Internet Protocol    IPM Impulses Per Minute    ISDN Integrated Service Digital Network    ISUP ISDN User Part    ITU-T International Telecommunications Union-Telecommunications    IWF Interworking Function    IXC Interexchange Carrier    LA-IWF Line Access Interworking Function    LA-CPS Line Access Call Processor Server    OAM&P Operations, Administration, Maintenance, and Provisioning    OC12 Optical Carrier level 12 signal (622 Mbps)    OC3 Optical Carrier level 3 signal (155 Mbps)    OPC Originating Point Code    OSS Operations Support Systems    PCM Pulse Code Modulation    PLA-IWF Private Line Interworking Function    PNNI Private Network-Network Interface    POTS Plain Old Telephone Service    PSTN Public Switched Telephone Network    PVC Permanent Virtual Connection    SS7 Signaling System 7    SSP Service Switching Point    STP Signal Transfer Point    STS1 Synchronous Transport Signal, level 1    SVC Switched Virtual Connection    TACPS Trunk Access Call Processing Server    TA-IWF Trunk Access Interworking Function    TDM Time Division Multiplexing    UBR Undefined Bit Rate    UNI User-to-Network Interface    VPI/VCI Virtual Path Identifier/Virtual Channel Identifier    VTOA Voice and Trunking over ATM    xDSL Digital Subscriber Line